Children’s Environmental Health

Children’s Environmental Health is the branch of pediatric medicine that studies the influence of the environment on children’s health, development and risk of disease (1). Children’s environmental health considers environmental exposures during pregnancy as well as exposures in infancy, childhood and adolescence. It studies parental environmental and occupational exposures that may influence the health of children. It traces the influence of early-life environmental exposures on health and development across the life span - from conception, through infancy, childhood and adolescence, and on into adult life and old age (2).

The core concept of children’s environmental health is that children are unique. Because they are passing through the early, formative stages of human development, children are qualitatively and quantitatively different from different from adults in their patterns of exposure and in their vulnerabilities to environmental hazards (3). The health consequences of environmental exposures in infancy and childhood are often very different from the consequences of exposures later in life.

Children’s environmental health is highly interdisciplinary and considers the environment broadly. It recognizes that children’s environments are complex, are comprised of many layers and change over the course of a child’s development. It therefore studies the influences on children’s health of chemical exposures in early life (4), the nutritional environment in the womb (2), the built environment (5), stress (6) and the social environment (7). It studies interactions among these multiple environments at different life stages, a broad view of the universe of children’s exposures termed the ‘exposome’ (8). It examines interactions between environmental exposures, poverty and social injustice (9). It examines the influences of the environment on the human genome and epigenome (10).

Children’s environmental health is inherently translational. It translates the findings of research into evidence-based blueprints for the prevention of disease and the protection of children’s health. The ultimate goals are to safeguard children’s health and to improve the environments where children live, learn and play.

Four great challenges confronting children’s environmental health discussed in this chapter are:

1. Rising rates of non-communicable disease among children worldwide. Environmental exposures are now known to be responsible in part for these increases. 2. Children’s exposure to thousands of inadequately tested chemicals of unknown hazard. 3. The global movement of toxic chemicals and hazardous waste from industrially developed countries to developing countries. 4. Inadequate training of physicians and other health professionals in environmental medicine, which results in missed diagnoses of environmental disease in children and lost opportunities for prevention and treatment.

Historical Origins of Children’s Environmental Health

Children’s environmental health arose in the second half of the 20th century through a convergence of scientific insights from three fields: pediatric toxicology, nutritional epidemiology, and social science research.

The Contributions of Pediatric Toxicology

Pediatric toxicology, the study of the effects of toxic chemicals on children’s health, is the oldest of the disciplines that have contributed to the formation of children’s environmental health. It derives many of its approaches and methodologies from toxicology and occupational medicine. Pediatric toxicology had its origins in clinical and epidemiologic studies of disease outbreaks in children that resulted from the dissemination of toxic chemicals, inadequately tested pharmacologic agents,

and other hazards into the environment where children were exposed. Typically these early episodes involved high-dose, acute exposures:

1. An epidemic of lead poisoning among children in

Queensland, Australia, in 1904. The source was found to be lead-based paint ingested by children playing on painted verandas (11). 2. An epidemic of leukemia among children in Hiroshima and Nagasaki exposed to ionizing radiation in the atomic bombings (12). Cases began to be seen in the first 2 to 3 years after the attacks. Incidence peaked approximately 7 years after the bombings and then declined. Risk was highest in the most heavily exposed children. 3. An increased risk of microcephaly among infants in Hiroshima and Nagasaki exposed to radiation in utero in the first trimester of pregnancy (13). The cause was radiation injury to the developing brain. There was no comparable damage observed in adults. 4. An epidemic of cerebral palsy, mental retardation, and convulsions among children in the remote fishing village of Minamata, Japan (14). This epidemic was traced to maternal ingestion during pregnancy of fish heavily contaminated with methylmercury. The source was a chemical factory that had discharged mercury-containing waste into

Minamata Bay. Mothers were physically unaffected. 5. A major epidemic of phocomelia, a previously rare birth defect of the limbs, in Europe in the 1950s and 1960s (15).

Clinical and epidemiologic studies found that the affected babies had been exposed in utero to thalidomide, a sedative prescribed to women during the first trimester of pregnancy to alleviate morning sickness. More than 10,000 cases were reported worldwide (8,000 of them in Germany) before thalidomide was removed from the market and the epidemic halted. Thalidomide was most harmful when taken between days 34 and 50 of pregnancy, precisely the time when the limbs form. Depending upon the timing of exposure, thalidomide was found also to be associated with defects of the eyes, ears, and heart as well as the alimentary and urinary tracts; it also was associated with an increased risk of autism. 6. Cases of adenocarcinoma of the vagina among young women who were exposed in utero to the synthetic estrogen diethylstilbestrol (DES), which had been prescribed to their mothers to prevent miscarriage (16). Incidence peaked in the years immediately after puberty. Mothers were physically unaffected.

These epidemics of disease of environmental origin in children established three principles that are fundamental to children’s environmental health:

1. They dispelled the myth that the placenta provides an impervious barrier and showed instead that toxic chemicals can cross the placenta to cause injury to the fetus. 2. They established that early-life exposures to toxic chemicals and other environmental hazards, including exposures in utero, can have devastating effects on children and that these effects can last lifelong. 3. They established that infants and young children have windows of developmentally determined vulnerability to toxic chemicals in which even extremely small exposures can cause devastating injury. These windows of vulnerability have no counterpart in adult life….

Recent research suggests that epigenetic modification of fetal gene expression based on metabolic cues received from the mother during pregnancy may be a mechanism of fetal programming that accounts at least in part for Barker’s observations and for the developmental origins of adult disease (22).

The Contributions of Social Science Research

Epidemiologic research in the social sciences is the third area of scientific inquiry that contributed to the growth of children’s environmental health (7). As a result of this research, exposure in utero to maternal stress and exposure in early childhood to traumatic events such as extreme violence, child abuse, rape, and incest are now understood to be able to increase risk of disease in childhood and across the life span (23). These studies demonstrate that psychosocial stress in early life is linked to a wide range of physical and mental illnesses, including asthma and obesity in childhood (24, 25) and depression, cardiovascular disease, and autoimmune disease in adult life (26)…

Growth of Research in Children’s Environmental Health

A further consequence of the 1993 NAS report and of the policy changes it stimulated was a substantial expansion in US federal research investment in children’s environmental health. As a result of this increased investment, the field has grown exponentially over the past two decades. Specific consequences are the following: • A national network of CEH and Disease Prevention

Research Centers was established with support from the

National Institute of Environmental Health Sciences (NIE-

HS) and the US EPA. Research in these centers has led to the discovery of numerous environmental risk factors for disease in children, including previously unrecognized developmental neurotoxicants, endocrine disruptors, and respiratory toxicants (33, 34). • A network of clinically oriented Pediatric Environmental

Health Specialty Units (PEHSUs) was established across the United States with support from the Centers for

Disease Control and Prevention (CDC)/Agency for Toxic

Substances and Disease Registry (ATSDR) and now also includes units in Canada, Mexico, Argentina, Uruguay, and Spain (35). • National and international conferences on CEH have been held since 1994 and have established and refined a research agenda for CEH. Sessions on CEH are now a major component of the annual meeting of the International

Society for Environmental Epidemiology. • Environmental Health Perspectives, the high-impact, peer-reviewed journal of NIEHS, has established a special section in each issue devoted to children’s environmental health. Since 1995 the number of articles in this section has increased by nearly 25-fold. • The American Academy of Pediatrics has published the

Handbook of Pediatric Environmental Health, known as the Green Book, now in its third edition (36). • The first Textbook on Children’s Environmental Health was published in 2013 (1). • Training programs have been launched to educate pedia-

tricians and research scientists in children’s environmental health (37). • Major prospective birth cohort epidemiologic studies have been launched in countries around the world to discover new associations between environmental exposures in early life and children’s health. These include the US

National Children’s Study (38), the Japan Environment and Children Study (39), the Avon Longitudinal Study of

Parents and Children in the UK (40), and the Norwegian

Mother and Child Cohort Study (41). To further increase statistical power for discovery of possible environmental causes of rare disease outcomes such as childhood malignancy, data from a number these birth cohorts are being pooled globally by the International Agency for Research on Cancer through their International Childhood Cancer

Consortium (42).

Children’s Environmental Health Today

The environment of the United States and in other developed countries has changed dramatically in the past two hundred years, and patterns of health and disease in children have changed in parallel…Today, in the aftermath of the epidemiological transition, non-communicable diseases are the major diseases confronting children in the United States, and they are on the rise: Asthma… birth defects… neurodevelopmental disorders… Leukemia…pre-term birth…obesity…

Evidence is mounting that harmful exposures in the environment are important causes of non-communicable diseases in children. Today, in consequence of the acceleration of research in children’s environmental health described above many links between disease in children and harmful exposures in the environment been discovered. Prospective birth cohort epidemiological studies have contributed greatly to these discoveries and have been especially effective in linking prenatal exposures to disease in childhood and beyond…

Evidence-Based Prevention of Environmental Disease in Children

A very exciting consequence of the discovery of environmental causes of disease in children is the successful translation of these discoveries into science-based blueprints for disease prevention…Removal of lead from gasoline, which resulted in a 90% reduction in blood lead levels of American children (Figure 1) (75);

These successful prevention programs have not only benefitted children’s health, but they have also benefitted the economy. Improvements in air quality in the United States are associated with estimated benefits of nearly $30 for every dollar invested (81). Removal of lead from gasoline has not only reduced lead poisoning by over 90%, but also has returned an estimated $200 billion to the US economy in every birth cohort born since 1980 through the increased economic productivity of more highly intelligent and creative children not impaired by lead (75).

Children’s Exposures to Synthetic Chemicals Today

Despite the great advances in knowledge and prevention of environmental disease in children described above, children today are exposed to thousands of manmade chemicals of unknown hazard. More than 85,000 chemicals are currently registered with the US Environmental Protection Agency (EPA) (4). These chemicals are used in millions of consumer products ranging from food packaging to clothing, building materials, motor fuels, cleaning products, cosmetics, medicinal products, toys and baby bottles. Most are new chemicals that did not exist 50 years ago….

A recurrent theme in all of these tragedies is that the new chemicals were brought to market with great enthusiasm, came into wide use and were widely disseminated in the environment with no premarket assessment. Then belatedly they were found to have harmful effects on health. Chemicals have simply been presumed to be safe and no systematic effort has been made to assess their potential toxicity.

A second repeated theme is that early warnings of danger have been ignored. As a result, efforts to control exposures and to prevent injury were delayed, sometimes for decades. In some instances, industries with deeply vested commercial interests in protecting markets for hazardous technologies, such as the lead, tobacco and asbestos industries, have actively opposed efforts to understand and control children’s exposures to these materials. These industries have used highly sophisticated disinformation campaigns to confuse the public and to discredit science (84). They have attacked heroic pediatricians and environmental scientists who called attention to the risks of emerging technologies and new chemicals.

A major unanswered question in children’s environmental health is whether there are additional chemicals in wide use today that pose unrecognized hazards to children’s health… Approximately twelve chemicals are known from clinical and epidemiologic studies to be developmental neurotoxicants in children, but another 200 chemicals have been shown to cause neurotoxicity in adult workers, and an another 1,000 are known to cause neurotoxic effects in experimental animals (85). It is not known how many of these 1,200 chemicals – some of which are currently in wide use – may pose neurotoxic hazards to infants and children.

The Global Export of Toxic Chemicals

Globalization of commerce has encouraged the relocation of polluting industries such as chemical manufacture, pesticide production and waste recycling from high-income countries to low- and middle-income countries (94). These industries are now booming in poor countries where labor costs are low and environmental regulations, worker protections, and public health infrastructure are often scant (95). Workers and communities in these countries are increasingly exposed to multiple

forms of pollution, often under highly unpredictable circumstances, and hazardous wastes are accumulating (96). The once very separate patterns of environmental contamination in developed and developing countries are converging.

Training Needs in Children’s Environmental Health

Physicians and other health care providers are critical to the recognition, management, and prevention of disease of environmental origin in children. The alert clinician is in a unique position to identify new associations between environmental exposures and pediatric disease and thus to initiate appropriate treatment and prevention (104)….

Informed suspicion is the principal tool for the correct diagnosis of environmental disease. The alert clinician needs to be open to the possibility that any child may have an illness that is caused or exacerbated by an environmental exposure. Because diseases of environmental origin in children seldom have unique physical signatures, the exposure history, supplemented by laboratory testing, is the principal diagnostic tool.

Unfortunately, diseases of environmental origin in children are underdiagnosed, and many are incorrectly ascribed to other causes. Opportunities for prevention and treatment are therefore lost. This reflects the fact that most physicians and other health care providers have not been adequately trained to take a history of environmental exposure or to recognize environmen-

Figure 3. Children at an E-Waste Recovery Site, South China tal exposures as a cause of illness in children.

Inadequate professional education is at the root of this problem. A 1985 survey of American medical schools found that the average US medical student received less than 4 hours of training in environmental and occupational medicine (105)…

Conclusion

Children’s environmental health is an exciting and expanding area of pediatric medicine. It offers opportunities for the discovery of new associations between environmental exposures and disease in children as well as opportunities for disease prevention.

Students, health professionals and others interested in obtaining more information on children’s environmental health or on career opportunities in the field can consult the following resources: • American Academy of Pediatrics, Council on Environmental Health. Available at: https://www.aap.org/en-us/aboutthe-aap/Committees-Councils-Sections/Council-on-Environmental-Health/Pages/default.aspx. • American Academy of Pediatrics. Handbook of Pediatric

Environmental Health. 3rd ed. Etzel RA, Balk SJ (editors).

Elk Grove Village, Ill: American Academy of Pediatrics; 2012. • Academic Pediatric Association, Special Interest group on

Environmental Health. Available at: http://www.ambpeds. org/specialInterestGroups/sig_env_health.cfm • Children’s Environmental Health Network. Avaialble at: http://cehn.org/wordpress/. • Environmental Health Perspectives, the peer-reviewed, open-access journal of the National Institute of Environmental Health Sciences regularly publishes articles on topics in children’s environmental health. Available at: http:// ehp.niehs.nih.gov/. • Textbook on Children’s Environmental Health. Landrigan

PJ, Etzel RA (editors). London: Oxford University Press, 2013 (1). • World Health Organization. Network of Collaborating

Centres for Children’s Environmental Health. Available at: http://www.niehs.nih.gov/research/programs/geh/partnerships/network/index.cfm.

About the Author

Dr. Philip Landrigan is a pediatrician and one of the world’s leading authorities on public health, particularly children’s health. He is Director of the Global Public Health and the Common Good Program at Boston College and Director of the Global Observatory on Pollution and Health at Boston College, and former Chair of the Department of Preventive Medicine at Mount Sinai School of Medicine. Dr. Landrigan spoke at the SCCMA Environmental Health Series on May 20, 2021 on “Children’s Environmental Health”. The recording of this Session 3 with Q and A can be found at http://www.sccma.org/resources/webinars/sccma-on-demand-webinars.aspx. This is an abbreviated article from his classic book “Children’s Environmental Health” (2013) that provides essential background on this topic and with key resources for pediatricians. The full 18-page article, which is quite compelling and inspiring, can be found at http://www.sccma.org/resources/programs/environmental-health.aspx.